Tornado shelters are important. “Most death and injuries in tornados result from individuals being struck by flying debris or being killed by being rolled across the ground by the high winds.” and “almost all the damage caused by tornadoes can be attributed to wind induced forces tearing structures apart.” By John Snow, “Tornado”, “Encyclopedia Britannica” 2011.
A conventional tornado shelter of the prior art can be a complicated structure requiring specific/special building materials, and skillful installation to resist impact from flying debris; heavy loading, to prevent collapse and, the capability of resisting both extensive wind shear and lift. Applied cost has several components including the tornado shelter structure itself, delivery to site, and on-site construction and installation. No prior reliable tornado shelter exists that can be easily delivered, and erected by unskilled labor on site at a low cost.
A new, improved type of tornado shelter therefore requires new materials, a different type of structure and simple installation. Conflicting requirements are building materials of relatively light weight for easy delivery, but a heavy structure for strength and stability. The new structure requires a different and corrected perception of the effect of wind on shelters.
Different types of structures are affected differently by wind. Extensive research of the literature suggested a geodesic dome type structure. Practical experience with a large dome in a high wind area (60-70 miles per hour) in Missouri reinforced that conclusion.
Computer wind simulations which included tests of wind shear, wind lift and load properties of various configurations of the geodesic dome tornado shelter using the computer program Solidworks Computational Fluid Dynamics (CFD were reviewed by specialized engineers to determine that the structure could a) handle wind shear of 350 miles per hour b) handle a large load of 20,000 pounds, c) deal with 10,000 pounds of lift and d) handle debris thrown at 100 miles an hour. These meet the requirements for an F4 as set by the FEMA 320 tests.
Most injuries caused during a tornado by wind driven debris either directly impacting a person or a sheltering structure, are caused by large items landing on top of them. Seemingly harmless items such as small rocks or larger items like a wooden two-by-four can become deadly projectiles.
In order to pass the stringent FEMA storm shelter projectile tests, shelters are typically made from dense and weighty materials like concrete and steel. Current, above ground designs are massive and heavy, and often use an obstructive barrier method to withstand the high winds of a tornado and deadly wind driven projectiles. Other shelter options are buried underground, which adds to the complexity of construction, installation, and extraction. Underground shelters also risk developing mold, flooding, or being covered by debris during a storm.
Some, more modern, shelters incorporate more modern composite materials, but in all cases, current shelters are expensive and require third-party, professional installation crews or heavy machinery for installation. Most above ground storm shelters start at about $3,000. As a result of such high cost, most homes in high storm areas do not have a storm shelter in spite of the variety of storm shelters available. Storm shelters are usually considered too expensive by many who would benefit from them but, at the same time, so desirable that a new trend in St Louis, Mo. s for engaged couples to request storm shelter donations as a wedding gift.
Communal storm shelters do exist in some communities, but often people don't seek shelter from a tornado without a direct visual indication of the impending hazard. Even then, if a large group of people try to relocate to a communal shelter at once, the influx of traffic can leave people stranded in their cars in a traffic jam—arguably one of the most dangerous places to be during a tornado. As a result of those risks, personal storm shelters are beneficial and in demand by consumers.
The present invention provides a solution to the above-noted problems by providing storm shelters that are constructed of lightweight, high impact materials and are affordable, easily transportable with a non-commercial vehicle/non-heavy goods vehicle, (such as a pick-up truck of average size), easy to erect, and easy to relocate.